Root pressure

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Root pressure is a mechanism used by vascular plants to transport water through the xylem to the plant's higher reaches. Due to the root's active absorption of dissolved nutrients, the water in the soil tends to be poorer in solutes than the water inside the root's cells. The resulting solute potential gradient causes water to flow into the roots through osmosis. Although the root pressure varies greatly between different species of plants (extreme examples include up to 145 kPa in Vitis riparia [1]), it is usually quite low. The main contributor to the water transportation is the Transpiration pull.

The endodermis in the root is important in the development of root pressure. Ions in the water can be actively secreted in the living cell. The endodermal cells secrete the ions into the cells around the xylem which in turn secrete them into xylem vessles

This creates a Water potential gradient and by osmosis, water diffuses fom the cortex, through the endodermis and into the xylem.

Therefore, root pressure is caused by this accumulation of water in the xylem.

Root pressure provides a force, which in effect, pushes water up the stem, but it is not enough to account for the movement of water to leaves at the top of trees

In some plants, on windless nights, root pressure causes guttation.de:Wurzeldruck nl:Worteldruk zh:根压